Magnesium base alloy



Patented Jul 26, 1938 John A. 'Gann, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Michigan No Drawing. Original application August 2, 1937,

Serial No. 156,941. Divided and this application February 3, 1938,

4 Claims.

The present invention relates to magnesium alloys and more particularly to those in which magnesium is the predominant constituent.

A large number of magnesium alloys have been developed and many of them have been used commercially. While certain of these alloys-have tensile strengths that are satisfactory for a wide variety of uses, their yield strengths are often so low that articles made from such alloys will de form readily and assume a large permanent set at a stress considerably below the stress corresponding to the ultimate tensile strength,

The principal object of my invention is to produce magnesium alloys having improved physical properties. A more specific object is to producev magnesium alloys having 'improved'ratios of yield strength to tensile strength. Other objects and advantages will appear as the description pro-' ce'eds.

The invention is based on the discovery that the magnesium-aluminum-cadmium alloys, as described in United States Patent No. 1,729,339, may be improved to a very marked extent by the addition of relatively small amounts of lead and that this alloy may be still further improved by the addition of relatively small amounts of at least one of the metals selected from the group, tin and zinc. I have likewise "discovered that maximum property improvement is obtained when these alloys are subjected to the well known methods 01- solution heat treatment and aging. I have found that these advantages occur when approximately 0.5 to 10 per cent of lead are added to the known magnesium-aluminum-cadmium alloy containing 1 to 12 per cent of aluminum and 1 to 10 per cent of cadmium, thereby producing my new magnesiliir aluminum-ejadmium-lead alloy. I have likewise discovered that the properties of this magnesium-aluminum-cadmium-lead alloy may be improved by adding approximately 0.5 to 8 per cent of at least one of the metals selected from the group of relatively low melting-point metals, tin and zinc. 7

The following tables give specific examples which illustrate the improvement in yield strength and in the ratio 01 yield strength to tensile strength of my new alloy as compared to Y the known magnesium-aluminum-cadmium alloys. I have likewise found that the increase in yield strength and in' the yield strength to tensile strength ratio, as given in these tables, is accompanied by an improvement in Brinell hardness amounting to approximately 25 per cent for the as cast alloys, 35 per cent for the solution heat Serial No. 188,460 (Cl. -168) treated alloys, and 55 per cent for the solution I heat treated and aged alloys.

Cast alloys Nominal composition 'i ggfiga Yield Tensile 'i ri strength, strength, strength lb./sq. in. ib./sq. in. to tensile Al ca Pb s11 Zn strength 2 8 6,200 25,900 0.24 2 8 10 8,400 26,000 .32 2 8 10 2 9,200 26, 200 .35 4 4 7, 400 27,200 127 4 4 2 8,800 28,500 .31 6 4 2 10,500 28,900 .36 6 4 2 13, 100 22,411) .58 6 4 2 13,200 27,300 .48 6 4 2 L..- 6 15,300 24,500 .63 8 2 12,000 25,000 .48 8 2 l 4 15, 200 23, 900 63 8 2 1 3 4 16,400 22, 700 72 8 2 1 5 4 17,100 22,100.v 77 4 6 6 2 3 1l,900 23,400 .51

Solution heat treated alloys Solution heat treated and aged alloys 2 8 26,000 .23 2 8 l0 8,100 25,800 .31 2 8 l0 2 10,200 25,000 .41 4 4 7,210 28,500 25 4 4 2 7.700 20.000 .27 6 -4 2 10, 100 31, 100 32 0 4 2 13,600 30.300 .45 6 4 2 18,000 34, 800 .52 6 4 2 6 23,300 28, 600 .82 8 2 14,200 32,000 .44' 8 2 l 4 23, 200 35, 400 .65 8 2 I 3 4 23.500 33,600 .70 8 2 1 5 4 23,300 32, 200 72 4 6 0 2 3 16, 400 30.000 .55

The specific proportions of each metal to be employed in these new alloys depends on the use for which the alloy is intended. In general, Iprefer' to use alloys containingmore than per cent of magnesium and lessthan 20 per cent Y of total added metals, but where the alloy is to be used for the productionjof wrought shapes generally, suitable compositions are those contaming more than 90 per cent of magnesium and 1 the production of wrought shapes by extrusion and forging, the. alloy should preferably contain 90 to 96 per cent 'of magnesium and the various alloying ingredients in the following'proportions:

1 to 8 per cent of aluminum, 1 to 3 per-cent of cadmium, 0.5 to 2 per cent of lead, 0.5 to 3 per cent of tin, and 0.5 to 2 per cent of zinc. If the alloy is to be fabricated by rolling rather than by extrusion or forging, the percentage of-aluminum should preferably lie within the range of 1 to 5 per cent.

My new'polynary alloys may be prepared by the-methods usually employed for melting and alloying metals with magnesium, such as adding the respective alloying metals singly or jointly to a bath of molten magnesium protected" from oxidation by a cover of fluid fihx. The solution heat treatment for the zinc-free alloys may consist in heating the material for 20 hours at: 430 0., followed by air cooling, or, when zinc is present in the alloy,,12 hours at 320 C. plus 16 hours at 420 C., followed by air cooling. The aging treatment consists of approximately 16 hours heating at 'C., subsequent to the above solution heat treatment. Plastic deformation operations, such as extruding, forging, and rolling are best conducted at temperatures between 300 and 400 C.

This application is a division of my co-pending application Serial No.156,941 flied August 2, 1937.

Other modesof applying the principle of my invention may be employed instead of those explained, change being made as regards the ingredients and the steps herein diselmd, provided those stated by any of the following claims or their equivalent be employed. p

I particularly point out and distinctly claim as my invention:----

1. A magnesium-base alloy containing about 1 to 12 per cent ofaluminum, about 1 to 10 per cent of cadmium, about 0.5 to 10 per cent of lead, and about 0.5 to 8 per cent of tin, the balance being magnesium. v

2. A magnesium-base alloy containing about 4 to 10 per cent of aluminum, about 2 to 8 per cent of cadmium, about 1 to 6 per cent of lead, and about 1 to 6 per cent of vtin, the balance being magnesium. I

3. A magnesium-base alloy containing about 1 to 8 per cent of aluminum, about 1 to 3 per cent of cadmium, about 0.5 to 2 per cent of lead, and

about 0.5 to. 3 per cent of tin, the balance being magnesium 4. A magnesium-base alloy containing about 6 percent of aluminum, 4 per cent of cadmium, 2 per cent of lead, and 6 per cent of tin, the balance being magnesium.

' JOHNA. GANN. 

